Like many others, I like to follow many low-carb and paleo bloggers and read what they have to say, and I’ve read numerous books on these topics. Interest in these topics is increasing and that’s understandable, given the dire nature of the obesity epidemic. No one who strives to improve himself wants obesity to happen to him (or her, either), and it’s pretty clear that eating habits will have to change if society is ever to put a dent in the obesity epidemic. But there’s an important sense in which we who are trying to stay healthy and fit need to be going beyond low carb and paleo diets.
Books and sites on either low carb or paleo diets often get into rather arcane discussions on the details of these diets and how they affect our health and metabolism. That’s all well and good, and I often enjoy these discussions and learn a great deal from them. There’s also a sense in which “mere” bloggers are trying to do science, by teasing out the implications of published reports.
But I wonder. Most of the people reading these discussions, or at any rate most people reading here, probably already know that they should limit their carbohydrate intake if they want to keep body fat low. They also know that vegetable oils do no one any good, that gluten often needs to be avoided, that protein intake should be optimal, and so on. I’m not at all disparaging discussion and investigation of low carb/paleo, but personally, I’ve already moved on.
I practice most of the principles espoused in this sphere already. Low carb and paleo give me my best chance, in my opinion, of avoiding heart disease, cancer, diabetes, and all the rest of the diseases of modern life, and the best chance of attaining my median lifespan, that is, my full statistical life expectancy. But what about maximum lifespan?
In studies that look at substances or processes that extend lifespan, researchers distinguish between median and maximum lifespan. If a substance, say resveratrol, or a process, say exercise or calorie restriction, extends lifespan, we want to know whether it is median or maximum lifespan that is extended. If they extend maximum lifespan, that means that some fraction of the test animals lived well beyond the age at which all the controls died; if median lifespan is extended, that means that the maximum lifespan of both groups was the same, but more of the test animals reached the median than did the controls.
The Jackson Laboratory, an independent aging research organization, says,
If a treatment prevents a single important cause of mortality without affecting the underlying senescence rate, that treatment is more likely to increase median life span than maximum life span. This is because the animal will die from the failure of another competing cause of mortality and will not live longer than what is normal for its cohort. On the other hand, if a treatment does retard underlying senescence rates, it has the potential to delay the expression of many age-related diseases — including those that constitute the competing causes of mortality — and, thereby, increase maximum life span for the cohort.
The following graph illustrates the distinction.
Greater median lifespan means that a particular disease or infirmity was avoided; greater maximum lifespan means that aging itself was slowed.
From current evidence, low carb and paleo diets will increase median, but not maximum, lifespan. And at this point, I’m more interested in my maximum lifespan, since I’m already doing just about everything that will increase my median lifespan.
Scientists hotly dispute various theories of aging, and there’s no general agreement on what causes it. However, the evidence increasingly makes it clear that aging is either programmed or quasi-programmed. Some animals appear to barely age at all, and there seems no reason why organisms couldn’t live forever, barring accidents or predation. This makes it unlikely that aging is mere degradation that an organism cannot overcome. Humans don’t age in any significant sense until maturity; our defense and repair mechanisms quickly come to the rescue of any damage.
But as we age, we lose our ability to repair ourselves. Evolution by natural selection just has not prevented our aging, or possibly has actively encouraged it in the interest of the species as a whole. (This is evolutionary heresy of course, a form of group selection. The heretical aspect is precisely the obstacle that has prevented scientists from seeing this.)
From this brief exposition of aging, it can be seen that doing everything in accordance with nature may not help you; nature wants you to die.
To enter the territory of maximum lifespan, we need to do things like lower myostatin, promote autophagy through fasting and chemical autophagy boosters, or possibly take n-acetylcysteine to lower oxidative stress. ( I say “possibly” because n-acetylcysteine has not been shown to increase lifespan.)
The substances and processes that do these things arguably do not fall under either of the categories of low carb or paleo. Weightlifting, fasting, resveratrol, metformin, curcumin: all these do not fit into conventional low carb/paleo thinking.
If you already stay fit and eat right, time to take one step beyond. Low carb and paleo definitely benefit health and prevent disease, but the other steps you take may well extend lifespan further.